iTrek USB Receiver ramdomly stops working

I hope some of you are using the iTrek USB Receiver. (details of my receiver here http://www.pocketgps.co.uk/itrekmouse.php )
Sometimes it works perfectly with map monkey, the red light on the receiver flashes and i get a good FIX. Other times the red light goes very dim and stays on but Map monkey can't connect to the receiver. This problem is killing me. I can't find the solution.